1. Field of the Invention
The present invention relates to thermally insulated building and roofing construction panels of the type formed by a pair of spaced apart metal skins and an interposed thermal insulation material and, more particularly, to such panels having an improved end and side-joint construction with a series of cooperating sealing strips for assembling such panels into a roof structure.
2. Description of the Prior Art
Building and roof construction panels having exterior metal facing sheets and an interposed interior core of a thermal insulation, such as polyurethane or polystyrene foam, or compressed wood or recycled wood fiber, are well known. Also well known are a variety of end and side joints for these panels. Some of these joints are designed to permit the fabrication of the panels with identical external top and bottom facing sheets so that the panel fabricator requires only a single roll-former line to produce these sheets. It is also known to produce panels with different end and side configurations to create a tongue and groove end/side structure to facilitate field erection of the finished panels. Further the use of hidden threaded or nailed fasteners to securely attach such panels and the use of supplemental metal clamping fixtures to retain the panels in position is also known.
One major shortcoming of the thermally insulated double-skinned metal panels of the prior art is their unsatisfactory performance in fire tests, especially when a polyurethane foam is used as the thermally insulating core material. While the thermal properties of such foams are excellent, their well known flammability requires that they be completely encapsulated in a fire resistant material such as the aluminum face sheets of the finished panel. Such encapsulation has proven to be surprisingly effective until the fire induces sufficient stress for the panel joints to fail and spring open to expose the core material to the flames. When this happens the entire panel will catastrophically fail. A panel joint which resists such disengagement will greatly enhance the complete panel fire rating.
A second shortcoming of many of the panels of the prior art is the relative inability of the petroleum pitch or tar, or the polymeric sealing materials used to withstand, over the long term, the environmental assaults of rain, sleet, hail, snow, ozone and other airborne chemicals and ultraviolet light so that, in time, they will fail and allow leakage of water into, and building heat out of, the failed joint areas. This is especially critical on flat roof installations where ponding at low points often allows substantial quantities of water to accumulate during a rainstorm. Under such circumstances, even a small pinhole can create a major leakage problem.
To obtain the longest possible lifetime of these roof panels requires great care to avoid application errors such as misalignments and sealer pinholes when assembling roofing panels in the field. This care tends to require both good weather during installation and a plurality of skilled workers to achieve the best results, and therefore, can be quite expensive. A panel joint which protects the joint sealing materials from environmental assault and subsequent failure will greatly enhance the final panel utility rating.
A third problem encountered in prior art panels has been the critical limiting strength of a roof assembled from such panels. Side and end joints have been the limiting considerations in establishing maximum panel width due to extreme expansion and contraction factors. By developing a stronger side and end joint structure which resists slippage and disengagement under stress, all of the problems noted above are substantially, if not totally, alleviated and other less critical parameters become controlling in determining final panel width. As a result panels having fewer joints can be economically produced. Construction costs are reduced, fire resistance rating is improved, and the long term environmental degradation of the panel system is reduced.
In addition, many prior art roof systems required that any previously used roofing system either be completely removed before they could be applied and/or that layers of a ballast or sealant materials such as a polymeric adhesive, tar, pitch or asphalt be used to hold them down. Use of ballast (as much as one (1) ton per 100 sq. ft.) greatly increases the support requirement of the building structure. A roofing system with structural value which does not have these limitations would significantly reduce costs by eliminating the need to remove and dispose of waste materials from the existing roof. This, in effect, causes the recycling of the existing roof materials, in place, by being able to apply the panel system over the existing materials. This ability greatly increases the ease with which the roofing system can be applied to particular construction applications thereby reducing costs and conserving landfill usage.